In March, the World Health Organization estimated that air pollution was responsible for 7 million premature deaths in 2012. That’s one out of every eight total deaths in the world.

Air quality has gotten worse over the last decade, and for more people. The 2014 Environmental Performance Index (EPI), a biennial global ranking that compares countries on high-priority environmental issues, shows that over the last decade, the number of people breathing unsafe air has risen by 606 million and now totals 1.78 billion. That’s one quarter of the global population.

But where are people suffering the worst air pollution, and how do we know? To help answer this question, we'vecompiled a map that shows national and city-level exposures to air pollutants that have the greatest effect on human health, fine particulate matter (PM2.5). PM2.5 originates from combustion of fuels from both mobile sources like vehicles and stationary sources, including power plants, industry, and household biomass burning. Although invisible to the human eye, PM2.5contributes to acute lower respiratory infections and other diseases such as cancer. It can penetrate human lung and blood tissue, leading to higher incidences of cardiovascular and lung disease.

The map overlays two sources of data on air pollution: for cities, the WHO’s recent release of its Ambient (outdoor) air pollution in cities database 2014; for countries, ground-level exposures to PM2.5 are derived from satellite measures in the 2014 EPI. For the first time, both national and city-level data can be compared to see how air pollution is distributed globally. Here are some observations we made using the map.

There are differences in where air pollution is being monitored.

Many countries still don't have ground-based monitors to measure fine particulate matter (PM2.5). Nearly 70 percent of the air monitoring stations are disproportionately located in wealthy countries. Especially in Africa, Southeast Asia, and South America, there are major gaps in monitoring. These are also areas that are industrializing pretty rapidly. Scientists predict that nearly half of the projected growth in urban areas by 2030 will be in China and India alone, while urban areas in Africa are expected to grow a whopping 590 percent from 2000 levels.

Many of these countries that are industrializing and urbanizing so quickly lack ground monitors and tools to communicate to citizens the dangers of different levels of exposure. India, for example, still lacks any index like the U.S.’s Air Quality Index that communicates daily health warnings of various levels of air pollution to the public.

Poor air quality affects all countries, regardless of wealth.

From the country-level data in the map, it’s easy to see that most countries in Europe have annual averaged exposures to PM2.5 that exceed levels the WHO deems as “safe” (i.e., 10 micrograms/cubic meter). Paris in March of this year had to impose major restrictions on motor vehicles when air pollution hit dangerously high levels. Salt Lake City in the United States regularly experiences severe smog in the winter time, leading to public health and economic concerns among residents there. What this troubling trend demonstrates is that there isn't an “Environmental Kuznets Curve” necessarily between wealth and air pollution: As countries get richer, we’re not seeing a decrease in air pollution, suggesting its severity as a global problem.

Cities have it worst.

Comparing the range of observed values between the country-level and city-level data, it’s easy to see that air pollution is worse in cities than when averaged across a whole country. New Delhi, the capital of India, for instance, is the city with the worst air pollution. Many other cities in South Asia, including in Pakistan, Iran, and Bangladesh, all suffer pollution levels more than 10 times higher than the safe threshold. These data further corroborate reports made earlier this year that suggested India, and in particular New Delhi, has severe air pollution that is often overlooked in lieu of China’s air pollution problem (see The New York Times, The Wall Street Journal, and Time).

While India’s air comes out worst among cities, China’s air quality at a national scale is the worst globally. Compared to India, part of this difference in results is due to the fact that China has more people living in cities (more than half) than India (around one-third). More people living in cities where air pollution is worse means more people exposed, which is reflected in the national aggregate average exposure numbers. In May 2014, China announced that it will remove 5 million older, polluting cars from roads, over half just in Beijing, to address air pollution problems, but the question remains as to whether this number is enough. Statistics for China’s vehicle ownership have grown exponentially over the last decade and topped 240 million at the end of 2012.

While this map provides a baseline understanding of air pollution in your city or country, it’s important to keep in mind that these data represent annual averages or longer term trends. Checking local readings of air pollution levels where available, particularly for groups sensitive to air pollution, such as those who suffer from asthma, can help one decide whether to limit outdoor activities on high-pollution days. Others have taken matters into their own hands, including a proliferation of smartphone apps that compile air quality data (like this one). A DIY home air pollution filter movement has also become popular in major cities in China.

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Five days after Hurricane Maria made landfall in Puerto Rico, its devastating impact is becoming clearer.

Five days after Hurricane Maria made landfall in Puerto Rico, its devastating impact is becoming clearer. Most of the U.S. territory currently has no electricity or running water, fewer than 250 of the island’s 1,600 cellphone towers are operational, and damaged ports, roads, and airports are slowing the arrival and transport of aid. Communication has been severely limited and some remote towns are only now being contacted. Jenniffer Gonzalez, the Resident Commissioner of Puerto Rico, told the Associated Press that Hurricane Maria has set the island back decades.

A small group of programmers wants to change how we code—before catastrophe strikes.

There were six hours during the night of April 10, 2014, when the entire population of Washington State had no 911 service. People who called for help got a busy signal. One Seattle woman dialed 911 at least 37 times while a stranger was trying to break into her house. When he finally crawled into her living room through a window, she picked up a kitchen knife. The man fled.

The 911 outage, at the time the largest ever reported, was traced to software running on a server in Englewood, Colorado. Operated by a systems provider named Intrado, the server kept a running counter of how many calls it had routed to 911 dispatchers around the country. Intrado programmers had set a threshold for how high the counter could go. They picked a number in the millions.

The greatest threats to free speech in America come from the state, not from activists on college campuses.

The American left is waging war on free speech. That’s the consensus from center-left to far right; even Nazis and white supremacists seek to wave the First Amendment like a bloody shirt. But the greatest contemporary threat to free speech comes not from antifa radicals or campus leftists, but from a president prepared to use the power and authority of government to chill or suppress controversial speech, and the political movement that put him in office, and now applauds and extends his efforts.

The most frequently cited examples of the left-wing war on free speech are the protests against right-wing speakers that occur on elite college campuses, some of which have turned violent.New York’s Jonathan Chait has described the protests as a “war on the liberal mind” and the “manifestation of a serious ideological challenge to liberalism—less serious than the threat from the right, but equally necessary to defeat.” Most right-wing critiques fail to make such ideological distinctions, and are far more apocalyptic—some have unironically proposed state laws that define how universities are and are not allowed to govern themselves in the name of defending free speech.

A growing body of research debunks the idea that school quality is the main determinant of economic mobility.

One of the most commonly taught stories American schoolchildren learn is that of Ragged Dick, Horatio Alger’s 19th-century tale of a poor, ambitious teenaged boy in New York City who works hard and eventually secures himself a respectable, middle-class life. This “rags to riches” tale embodies one of America’s most sacred narratives: that no matter who you are, what your parents do, or where you grow up, with enough education and hard work, you too can rise the economic ladder.

A body of research has since emerged to challenge this national story, casting the United States not as a meritocracy but as a country where castes are reinforced by factors like the race of one’s childhood neighbors and how unequally income is distributed throughout society. One such study was published in 2014, by a team of economists led by Stanford’s Raj Chetty. After analyzing federal income tax records for millions of Americans, and studying, for the first time, the direct relationship between a child’s earnings and that of their parents, they determined that the chances of a child growing up at the bottom of the national income distribution to ever one day reach the top actually varies greatly by geography. For example, they found that a poor child raised in San Jose, or Salt Lake City, has a much greater chance of reaching the top than a poor child raised in Baltimore, or Charlotte. They couldn’t say exactly why, but they concluded that five correlated factors—segregation, family structure, income inequality, local school quality, and social capital—were likely to make a difference. Their conclusion: America is land of opportunity for some. For others, much less so.

One hundred years ago, a retail giant that shipped millions of products by mail moved swiftly into the brick-and-mortar business, changing it forever. Is that happening again?

Amazon comes to conquer brick-and-mortar retail, not to bury it. In the last two years, the company has opened 11 physical bookstores. This summer, it bought Whole Foods and its 400 grocery locations. And last week, the company announced a partnership with Kohl’s to allow returns at the physical retailer’s stores.

Why is Amazon looking more and more like an old-fashioned retailer? The company’s do-it-all corporate strategy adheres to a familiar playbook—that of Sears, Roebuck & Company. Sears might seem like a zombie today, but it’s easy to forget how transformative the company was exactly 100 years ago, when it, too, was capitalizing on a mail-to-consumer business to establish a physical retail presence.

The foundation of Donald Trump’s presidency is the negation of Barack Obama’s legacy.

It is insufficient to statethe obvious of Donald Trump: that he is a white man who would not be president were it not for this fact. With one immediate exception, Trump’s predecessors made their way to high office through the passive power of whiteness—that bloody heirloom which cannot ensure mastery of all events but can conjure a tailwind for most of them. Land theft and human plunder cleared the grounds for Trump’s forefathers and barred others from it. Once upon the field, these men became soldiers, statesmen, and scholars; held court in Paris; presided at Princeton; advanced into the Wilderness and then into the White House. Their individual triumphs made this exclusive party seem above America’s founding sins, and it was forgotten that the former was in fact bound to the latter, that all their victories had transpired on cleared grounds. No such elegant detachment can be attributed to Donald Trump—a president who, more than any other, has made the awful inheritance explicit.

National Geographic Magazine has opened its annual photo contest, with the deadline for submissions coming up on November 17.

National Geographic Magazine has opened its annual photo contest for 2017, with the deadline for submissions coming up on November 17. The Grand Prize Winner will receive $10,000 (USD), publication in National Geographic Magazine and a feature on National Geographic’s Instagram account. The folks at National Geographic were, once more, kind enough to let me choose among the contest entries so far for display here. The captions below were written by the individual photographers, and lightly edited for style.

What the Trump administration has been threatening is not a “preemptive strike.”

Donald Trump lies so frequently and so brazenly that it’s easy to forget that there are political untruths he did not invent. Sometimes, he builds on falsehoods that predated his election, and that enjoy currency among the very institutions that generally restrain his power.

That’s the case in the debate over North Korea. On Monday, The New York Timesdeclared that “the United States has repeatedly suggested in recent months” that it “could threaten pre-emptive military action” against North Korea. On Sunday, The Washington Post—after asking Americans whether they would “support or oppose the U.S. bombing North Korean military targets” in order “to get North Korea to give up its nuclear weapons”—announced that “Two-thirds of Americans oppose launching a preemptive military strike.” Citing the Post’s findings, The New York Times the same day reported that Americans are “deeply opposed to the kind of pre-emptive military strike” that Trump “has seemed eager to threaten.”

More comfortable online than out partying, post-Millennials are safer, physically, than adolescents have ever been. But they’re on the brink of a mental-health crisis.

One day last summer, around noon, I called Athena, a 13-year-old who lives in Houston, Texas. She answered her phone—she’s had an iPhone since she was 11—sounding as if she’d just woken up. We chatted about her favorite songs and TV shows, and I asked her what she likes to do with her friends. “We go to the mall,” she said. “Do your parents drop you off?,” I asked, recalling my own middle-school days, in the 1980s, when I’d enjoy a few parent-free hours shopping with my friends. “No—I go with my family,” she replied. “We’ll go with my mom and brothers and walk a little behind them. I just have to tell my mom where we’re going. I have to check in every hour or every 30 minutes.”

Those mall trips are infrequent—about once a month. More often, Athena and her friends spend time together on their phones, unchaperoned. Unlike the teens of my generation, who might have spent an evening tying up the family landline with gossip, they talk on Snapchat, the smartphone app that allows users to send pictures and videos that quickly disappear. They make sure to keep up their Snapstreaks, which show how many days in a row they have Snapchatted with each other. Sometimes they save screenshots of particularly ridiculous pictures of friends. “It’s good blackmail,” Athena said. (Because she’s a minor, I’m not using her real name.) She told me she’d spent most of the summer hanging out alone in her room with her phone. That’s just the way her generation is, she said. “We didn’t have a choice to know any life without iPads or iPhones. I think we like our phones more than we like actual people.”

Senators Lindsey Graham and Bill Cassidy sparred with Bernie Sanders and Amy Klobuchar on CNN hours after their bill dismantling Obamacare appeared to collapse.

Ordinarily, you debate to stave off defeat. But for Senators Lindsey Graham and Bill Cassidy on Monday night, the defeat came first.

By the time the two GOP senators stepped on CNN’s stage Monday night for a prime-time debate over their health-care proposal, they knew they had already lost.

A few hours earlier, Senator Susan Collins became the third Republican to formally reject the pair’s legislation to repeal and replace the Affordable Care Act, effectively killing its chances for passage through the Senate this week. Graham and Cassidy had hoped to use the forum to make a closing argument for their plan, and to line it up against Senator Bernie Sanders and his call for a single-payer, “Medicare-for-All” health-care system. Instead, the two senators found themselves defending a proposal that was no less hypothetical—and probably much less popular—than Sanders’s supposed liberal fantasy.